Cottonbush

Narrow leaf Cottonbush

Narrow leaf Cottonbush is a plant native to South Africa and introduced to Australia as a garden plant but is now an invasive weed around Perth. In most parts of the state it is a declared weed. It is now well established in Roleystone and its range and abundance is increasing annually. Widespread in parts of the Araluen Estate, it can be seen in thick groves along the southern side of the Canning Valley along the walk trail from Thompson Road to Heritage Drive.

It is quite easy to identify by its inflated round, papery, green fruit pods that are covered in soft spines and turn brown with age. It has small, white to cream colored flowers and flowers all year round. Seeds are large and black, with a parachute of fine white hairs. In mid-summer, when the seeds are maturing in abundance they blow all around the valley and the ground is covered in the white wispy parachutes.

If you walk along the track now and have a close look at the plants you are likely to see the brightly colored larvae of the Wanderer Butterfly that live on the plants. This butterfly is also an introduced species (from North America) and although it lives on the cottonbush, does not reach large enough numbers to control it. If you look even closer you may be lucky enough to see a blue-green chrysalis with golden highlights hanging from a stem.

How to control

The plant is poisonous and may cause deaths in livestock if mixed in hay. Cottonweed invades run down or low fertility pastures and eventually forms dense thickets about 2m high.

The Department of Agriculture has put out a great summary of the control methods that can be downloaded from here. FN043_2003.pdf bytes

Control of Cotton bush is best done during it's main growing season of spring and summer. Narrow-leaf cotton bush has a shallow root system so small infestations can be dealt with by hand pulling - make sure you get all the roots to prevent suckering.

Take appropriate measures to avoid contact with the toxic sap, such as wearing rubber gloves and overalls, and washing hands thoroughly before eating. Contact with the sap could cause a rash or other symptoms for which medical advice should be sought.

Destroy any seeds in a way to avoid spreading the plant. When the ground is moist, it can be quite easily pulled up but this gets more difficult in summer. Larger infestations are best dealt with by a combination of spraying, slashing and pasture management.